Apparatus and method for removal of ions

ABSTRACT

An apparatus to remove ions including a plurality of capacitive electrode stacks. Each capacitive electrode stack may have: a plurality of first electrodes including a plurality of first current collectors; a plurality of second electrodes including a plurality of second current collectors; and a spacer between the first and second electrodes to allow water to flow in between the electrodes. The second current collectors of a first of the plurality of capacitive electrode stacks may be connected to the first current collectors of a second of the plurality of capacitive electrode stacks.

This application is a continuation of U.S. patent application Ser. No.14/351,857, filed Apr. 14, 2014, which is a national stage of U.S.national phase of PCT/NL2012/050716, filed Oct. 12, 2012, which claimsthe benefit of priority of Dutch patent application no. 2007598, filedOct. 14, 2011, each of the foregoing applications is incorporated hereinits entirety by reference.

FIELD

An embodiment of the invention relates to an apparatus to remove ioncomprising a plurality of capacitive electrode stacks, each electrodestack comprising: a plurality of first electrodes comprising a pluralityof first current collectors; a plurality of second electrodes comprisinga plurality of second current collectors; and a spacer between the firstand second electrodes to allow water to flow in between the electrodes.

BACKGROUND

In recent years one has become increasingly aware of the impact of humanactivities on the environment and the negative consequences this mayhave. Ways to reduce, reuse and recycle resources are becoming moreimportant. In particular, clean water is becoming a scarce commodity.Therefore, various methods and devices for purifying water have beenpublished.

A method for water purification is by capacitive deionisation, using anapparatus provided with a flow through capacitor (FTC) to remove ions inwater. The FTC functions as an electrically regenerable cell forcapacitive deionisation. By charging electrodes, ions are removed froman electrolyte and are held in electric double layers at the electrodes.The electrodes may be charged with a voltage between 0.5 to 2 Volts. Theelectrodes may be (partially) electrically regenerated to desorb suchpreviously removed ions without adding chemicals.

The apparatus to remove comprises one or more pairs of spaced apartelectrodes (a cathode and an anode) and a spacer, separating theelectrodes and allowing water to flow between the electrodes. Theelectrodes are provided with current collectors or backing layers thatare generally adjacent to or very near the electrodes and a material tostore the ions. Current collectors are electrically conductive andtransport charge in and out of the electrodes.

The apparatus may comprise a housing comprising an inlet to let waterinto the housing and an outlet to let water out of the housing. In thehousing, the layers of electrodes and spacers are stacked in a“sandwich” fashion by compressive force, normally by mechanicalfastening.

SUMMARY

A problem with the apparatus to remove ions is that the chargingvoltages may be low causing high electrical currents within theapparatus which may lead to increased energy loss or which may requirethe use of thick expensive metal connectors, or expensive power suppliesthat may handle high currents at low voltage.

It is an object to provide an improved apparatus to remove ions.

Accordingly, in an embodiment of the invention, there is provided anapparatus to remove ions comprising a plurality of capacitive electrodestacks, each capacitive electrode stack comprising:

a plurality of first electrodes comprising a plurality of first currentcollectors;

a plurality of second electrodes comprising a plurality of secondcurrent collectors; and

a spacer between the first and second electrodes to allow water to flowin between the electrodes,

wherein the plurality of second current collectors of a first of theplurality of capacitive electrode stacks are electrically connected tothe plurality of first current collectors of a second of the pluralityof capacitive electrode stacks.

By connecting the plurality of second current collectors of a first ofthe plurality of capacitive electrode stacks electrically to theplurality of first current collectors of a second of the plurality ofcapacitive electrode stacks, the electrical currents in the currentcollectors of a first of the plurality of capacitive electrode stacksmay be substantially the same as the electrical currents in the currentcollectors of a second of the plurality of capacitive electrode stacks,whereas the applied voltages will be divided over the plurality ofcurrent collectors of the first and second of the plurality ofcapacitive electrode stacks. This allows for an operation of theapparatus to remove ions at higher voltages, whereby the electricalcurrents may be kept relatively low.

The plurality of second current collectors of the second of theplurality of capacitive electrode stacks may be electrically connectedto the plurality of first current collectors of a third of the pluralityof capacitive electrode stacks.

The apparatus may comprise a housing, an inlet to let water enter aninterior of the housing, and an outlet to let water out of the interiorof the housing, and the plurality of second current collectors of thefirst of the plurality of capacitive electrode stacks, which areelectrically connected to the plurality of first current collectors ofthe second of the plurality of capacitive electrode stacks within thesame housing.

The plurality of first and second current collectors may be directlyelectrically connected by pressing them against each other.

The apparatus may comprise a clamp to press the plurality of currentcollectors against each other to electrically connect the plurality offirst and second current collectors.

The clamp may be of a non-metal material. The current collectors may bemetal free. The current collectors may comprise carbon, such as e.g.graphite to conduct an electrical charge.

The apparatus may comprise a first power connector to connect theplurality of first current collectors of the first stack with a powersupply.

The apparatus may comprise a second power connector to connect theplurality of second current collectors of the last of the plurality ofstacks with a power supply.

The power connector may be connected in series with the plurality offirst current collectors of the first of the plurality of capacitiveelectrode stacks and with the plurality of second current collectors ofa last of the plurality of capacitive electrode stacks.

The power connector may be provided with a metal and a carbon portion.

The apparatus may comprise a power connector clamp configured to pressthe current collectors against the carbon portion of the powerconnector.

The apparatus may comprise an insulator between each capacitiveelectrode stack in order to electrically insulate the stacks from eachother. The insulator may comprise a tray configured to hold the stack.

The apparatus may comprise a second insulator substantially surroundingthe current collectors so as to electrically insulate the currentcollectors.

The first current collectors of the plurality of first currentcollectors of the individual stacks may be electrically connected witheach other in parallel.

The first current collectors of the plurality of first currentcollectors may be electrically connected by clamping them together.

The apparatus may comprise a housing, an inlet to let water enter aninterior of the housing, and an outlet to let water out of the interiorof the housing, wherein the power connector provides an electricalconnection between the current collectors and the power source outsideof the housing.

The second current collectors of the first of the plurality ofcapacitive electrode stacks may be directly electrically connected tothe first current collectors of the second of the plurality ofcapacitive stacks.

The plurality of current collectors within the electrode stack may beelectrically connected in parallel.

According to a further embodiment of the invention, there is provided anapparatus to remove ions comprising a plurality of electrode stacks,each electrode stack comprising:

a plurality of first electrodes comprising a plurality of first currentcollectors;

a plurality of second electrodes comprising a plurality of secondcurrent collectors;

a spacer between the first and second electrodes to allow water to flowin between the electrodes; and

a power connector configured to connect a power source to the pluralityof capacitive electrode stacks in electrical serial connection with eachother and the resistivity in each of the capacitive electrode stacks issubstantially equal so as to divide the potential difference as appliedby the power source substantially equally over all capacitive electrodestacks.

The apparatus may comprise a housing, an inlet to let water enter aninterior of the housing, and an outlet to let water out of the interiorof the housing, wherein the capacitive electrode stacks are seriallyconnected within the housing.

The electrical current going through the second electrode of the firstcapacitive electrode stack may be equal to the electrical current goinginto the first electrode of the second capacitive electrode stack.

The capacitive electrode stacks that are in electrical serial connectionwith each other may be placed in the same housing

The plurality of second current collectors of the first of the pluralityof capacitive electrode stacks may be directly connected to theplurality of first current collectors of the second of the plurality ofcapacitive electrode stacks.

The apparatus may comprise a pressure device to provide compression ofthe stacks such that the pressure on each of the stacks is equal.

According to yet a further embodiment, there is provided a method ofmanufacturing an apparatus to remove ions, the method comprising:

providing a plurality of capacitive electrode stacks, each capacitiveelectrode stack manufactured by:

providing a plurality of first electrodes comprising a plurality offirst current collectors,

providing a plurality of second electrodes comprising a plurality ofsecond current collectors, and

providing a spacer between the first and second electrodes to allowwater to flow in between the electrodes; and

connecting the plurality of first current collectors of a first of theplurality of capacitive electrode stacks to the plurality of secondcurrent collectors of a second of the plurality of capacitive electrodestacks.

These and other aspects, features and advantages will become apparent tothose of ordinary skill in the art from reading the following detaileddescription and the appended claims. For the avoidance of doubt, anyfeature of one aspect of the present invention may be utilised in anyother aspect of the invention. It is noted that the examples given inthe description below are intended to clarify the invention and are notintended to limit the invention to those examples per se. Similarly, allpercentages are weight/weight percentages unless otherwise indicated.Numerical ranges expressed in the format “from x to y” are understood toinclude x and y. When for a specific feature multiple ranges aredescribed in the format “from x to y”, it is understood that all rangescombining the different endpoints are also contemplated.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the invention will be described, by way of example only,with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1 shows a schematic cross-section of an apparatus to remove ionsaccording to an embodiment;

FIG. 2 shows a schematic cross-section along the line Y-Y of theapparatus of FIG. 1;

FIG. 3 shows a schematic three dimensional figure of an apparatus toremove ions according to a further embodiment;

FIG. 4 schematically depicts a connector according to an embodiment;

FIG. 5 schematically depicts the connector of FIG. 4 in a ring of ahousing;

FIG. 6 schematically shows a full ring for the housing of an apparatusto remove ions with two connectors of FIG. 4;

FIG. 7 schematically depicts the stack of FIG. 3 wherein stack A, B areprovided in a tray;

FIG. 8 schematically depicts the apparatus after a first housing portionand the ring of FIG. 5 are provided;

FIG. 9 schematically shows a cross section of the apparatus of FIGS. 3to 7;

FIG. 10A and FIG. 10B schematically show a pressure plate according toan embodiment; and

FIG. 11A, FIG. 11B, FIG. 11C and FIG. 11D schematically show a top viewof a tray 113 a for use in an embodiment.

DETAILED DESCRIPTION

FIG. 1 shows a schematic cross-section of an apparatus to remove ionsfrom water according to an embodiment, which comprises two capacitiveelectrode stacks of first electrodes 13 and second electrodes 15separated by spacers 11. The apparatus may have a housing comprising afirst housing part 1 and a second housing part 3 made of a relativelyhard material e.g. a hard plastic. By pressing the first and secondhousing parts onto each other, for example with a bolt and nut (notshown) the housing may be made water tight. Adhesive, seals or O-ringsmay be used to improve the water tightness of the housing.

The housing is provided with an inlet 7 and an outlet 9. During ionremoval from the water, the water will flow from the inlet 7 to theoutlet 9 through the spacers 11 which separate the first and secondelectrodes from each other. In the example the current collectors of theelectrodes of two different stacks are clamped together inside thehousing. In principle the current collectors can be clamped eitherinside or outside the housing. Nevertheless, clamping the currentcollectors inside the housing may have an advantage that stacks can beplaced electrically in series without the need to make holes in thehousing, which helps to provide a water leakage free apparatus. Bycreating an electrical potential difference between the first and secondelectrodes, for example by applying a positive voltage to the firstelectrode (the anode) 13 and a negative voltage to the second electrode(cathode) 15, anions in the water flowing through the spacer 11 areattracted to the first electrode and cations are attracted to the secondelectrode. In this way the ions (anions and cations) can be removed fromthe water flowing through the spacer 11. The electrical potentialdifference can also be created by e.g. applying a positive voltage tothe first electrode (the anode) 13 and a lower positive voltage to thesecond electrode (cathode) 15. Also in this way the ions (anions andcations) can be removed from the water flowing through the spacer 11. Inthe example of FIG. 1 the two capacitive electrode stacks areelectrically placed in series, whereas the flow paths, which aredetermined by the spacers 11 are placed parallel, which means that thewater may flow from the inlet 7 to the outlet 9 via any of the flow pathof either the first or the second stack, which is placed in the samehousing.

The electrical potential differences between the first and secondelectrodes of the first capacitive electrode stack may be rather low,for example lower than 2 volts, lower than 1.7 volts or lower than 1.4volts. An advantage of placing FTC stacks electrically in series is thatthe potential difference over multiple capacitive electrode stacks maybe higher than that between the first and the second electrodes. Forexample, the potential difference over two capacitive electrode stacks Aand B, provided with first and second electrodes 13A, 13B, 15A, 15B anda spacer 11, which are electrically connected in series may be twice ashigh than the potential difference over one single capacitive electrodestack or two capacitive electrode stacks A and B which are placed in aparallel electrical circuit. The current collectors of the firstelectrode 13A of a first capacitive electrode stack may be connected toan electrical power source PS for example and the current collector ofthe second electrode 15A of the first capacitive electrode stack may beconnected to the current collector of the first electrode 13B of thesecond capacitive electrode stack. The connection may be directly, andmay, for example, be accomplished by clamp 17, which may be made from anon-electrically conductive material since its function is to press theconductive current collectors of the second and first electrode 15A, 13Btogether so that the current is directly transported between the twocurrent collectors. Alternatively clamp 17 may be made from anelectrically conductive material or may contain parts that areelectrically conductive. The second electrode 15A of a first capacitiveelectrode stack may substantially have the same potential as the firstelectrode 13B of the second capacitive electrode stack. The currentcollectors of the second electrode 15B may also be connected to theelectrical power source PS in order to complete the electrical circuit.

The current collectors of the first electrode 13A are clamped betweenclamp portions 19. The clamp portions 19 may be made from plastic, butcould also be made from carbon, for example graphite blocks. The clampportions 19 may be provided with a ratchet mechanism to secure the clampportions 19 with respect to each other and to optimize the contactsurface between the current collector 13A and the clamp portions 19 tooptimize electrical conductivity. To make the first connector, two clampportions 19 may be pressed against multiple current collectors of thefirst electrode 13A so as to press the current collectors together andprovide an electrical connection. Subsequently, an adhesive may be usedto permanently fix the clamp portions 19 with the current collectors ina watertight manner. Alternatively, a screw 21 may be used to press thecurrent collectors 13 together with the clamp portions 19 and at thesame time avoiding water metal contact of the connector. For a lowelectrical resistance it is advantageous to make the contact surface ofthe current collector and the connector of the same or similar material,for example carbon. An advantage of carbon is that it does not corrodein the water and that it is relatively cheap compared to othernon-corrosive materials and metals.

The pressure to clamp the current collector onto the connector may be atleast 0.1 bar, at least 0.5 bar and less than 15 bar, less than 10 baror less than 5 bar. The connector 18 may be glued against the housing soas to avoid contact of the water in the housing with the screw 21 whichmay be made out of metal. In this way corrosion of the screw may beprevented. In a similar way the current collector of the secondelectrode 15B of the second stack may be connected to the power sourcePS with a second connector 20. The potential difference delivered by thepower source PS between the current collectors of the first electrode13A of the first capacitive electrode stack via first cable 23 and thecurrent collector of the second electrode 15B of the second capacitiveelectrode stack via second cable 22 may be, for example lower than 4volts, lower than 3.4 volts or lower than 2.8 volts.

A potential problem of the relatively high potential difference betweenthe first and second connectors, 18, 20 may be a potential leak currentbetween the first and the second connectors. This may be prevented byplacing an insulator between the two connectors. This insulator 24 mayalso be placed between the two connectors as well as the first andsecond stack. The insulator 24 may be an insulator to prevent electricaland/or ionic transport. By placing the capacitive electrode stackselectrically in series, the applied potential difference between thefirst and second connectors 18, 20 may be increased or even doubled,whereas at the same time the current through the cables 22, 23 may bereduced by as much as 50%. The energy efficiency of the FTC apparatusmay therefore be improved and the need for very thick expensive cablesmay be reduced. At the same time a cheaper power source PS may be usedthat transports less current at higher voltage.

By assuring that the electrical resistance of the first and secondcapacitive electrode stacks A and B are substantially the same, thepotential difference as delivered by the PS may be equally divided overthe first and second capacitive electrode stacks A, B. As a consequencethe potential difference between the first electrode 13A and the secondelectrode 15A of the first capacitive electrode stack A may besubstantially the same as the potential difference between the firstelectrode 13B and the second electrode 15B of the second capacitiveelectrode stack B. This potential difference may for example be lowerthan 2 volts, lower than 1.7 volts or lower than 1.4 volts.

A feed through or opening may be provided through the housing at aposition where the first and second connectors 18, 20 are positionedagainst the housing 1,3. The feed through may be provided with a metalscrew 21 on which the cable 23 may be connected to the electrical powersource PS. The power source PS may be controlled by controller CN tocontrol the operation of the apparatus to remove ions.

The electrodes may be made substantially metal free to keep themcorrosion free in the wet interior of the housing and at the same timecheap enough for mass production. The electrodes may be produced from acurrent collector 13A, B, 15A, B provided with a substantially metalfree electrically conductive high surface area layer, which may containactivated carbon, carbon nanotubes, carbon aerogel, carbon black and/orgraphene on both sides which are in contact with the water. The highsurface area layer may be provided as a coating onto the currentcollector or as a separate film. A high surface area layer is a layerwith a high surface area in square meters per weight of layer materiale.g., >500 m²/gr.

If the electrodes are saturated with ions the electrodes may beregenerated by reducing or even reversing the potential difference anddischarging the electrical charge on the electrodes. This may result inthe release of ions from the electrodes into the water flowing throughthe spacer. The increased ion content in the water in the spacer can beflushed out of the spacer. Once most ions are released from theelectrodes and the water with increased ion content is flushed out ofthe spacer the electrodes are regenerated and can be used again forattracting ions.

FIG. 2 discloses the cross-section along line Y-Y of the apparatus ofFIG. 1. It shows the clamp 17 clamping the current collectors of thefirst and second electrode 15A and 13B (see FIG. 1). The housing isprovided with a space 25 to allow water to flow around the electrodesand the spacers 11 and a second passage 27 to allow water to collectfrom all the spacers 11 and flow through the outlet 9 (of FIG. 1). Theconnector 18 to connect the current collector of the first electrode 13Ais also shown. FIG. 1 is a cross section along the line Z-Z of FIG. 2.

FIG. 3 shows a schematic three dimensional figure of an apparatus toremove ions according to a further embodiment with 12 capacitiveelectrode stacks A, B, C, D . . . . Each capacitive electrode stack A,B, C, D . . . comprises a first electrode 13A, 13B, 13C, 13D, . . . anda second electrode 15A, 15B, 15C, 15D, . . . . The capacitive electrodestacks are provided with an opening 27 to allow water to enter or exitthe capacitive electrode stacks. A first group 31 of capacitiveelectrode stacks A . . . F is connected in series and a second group 33of capacitive electrode stacks G . . . L is also connected in series.The potential difference that may be applied between the first electrode13A of the first capacitive electrode stack A and the second electrode15F of the last capacitive electrode stack F of the first group may be 6times the potential difference of a single capacitive electrode stack.The potential difference between the first electrode 13A of the firststack A and the second electrode 15F may therefore be for example lowerthan 12 volts, lower than 9.4 volts or lower than 8.4 volts. Clamps (notshown) may be used to press the current collector of a second electrode15A to a current collector of a first electrode 13B.

FIG. 4 schematically depicts a connector according to an embodiment. Theconnector 41 may be used to connect a current collector of the apparatusto remove ions to a power source with a cable or lead 43. The connector41 may be provided with a closing off portion or contact member 47 to beplaced in the housing to close off an opening in the housing of theapparatus. The connector 41 may be provided with a connector surface orcontact face 45 defined in a head 46 of a contact portion adjacent tothe interior of the housing which may be pressed against the currentcollector to provide an electrical contact. The closing off portion orcontact member 47 of the connector 41 may be provided with carbon suchas graphite so as to avoid corrosion and to provide a good electricalcontact with the carbon current collector of the electrodes. Theconnector 41 may comprise a flexible material or seal 49 to provide awatertight connection with the housing. The seal 49 may be an O-ring,for example made of rubber to provide a water tight connection with thehousing. The cable or lead 43 may be provided in a connector portionhaving a neck 42 extending from the head in a direction away from thecontact face and having a receptacle at a dry surface 48 of theconnector portion so as to avoid corrosion of the cable or lead 43. Thelead or cable 43 may be engaged with the neck of the connector portionand is capable of directing an electrical current to the contact membervia the head. The contact portion is configured to engage with the stackso that the contact member is in electrical communication with thestack. The contact portion may be substantially cylindrical and maydefine the contact face 45. The perimeter of the contact face may forman arcuate rim. The contact portion may include a recess inward of theperimeter and a protrusion extending from the recess that terminatessubstantially coplanar with the rim. The contact face and the protrusionmay be substantially cylindrical. The housing further may have a recessproximate to the opening, and the contact portion may be seated in therecess. The connector or contact member 47 is press fit or adhered tothe opening. A seal portion may be defined by the head and/or neck suchthat the seal portion establishes a hydraulic seal between the sealportion and a mount into which the electrical connector is seated duringoperation.

FIG. 5 schematically depicts the connector of FIG. 4 provided in a ring51 of the housing. The ring is provided with a connector clamp 53 toclamp the electrode against the surface 45 of the connector. Theconnector clamp 53 may comprise a fixed part or protrusion member 55which extends from an interior surface of the housing and may comprise apair of arms. The connector clamp 53 may be made from plastic. e.g.polyethylene, polypropylene or polyvinylchloride. By making theconnector clamp 53 from plastic the connector clamp may press theplurality of current collectors onto the contact surface without beingsensitive to corrosion. A non-plastic connector clamp may be sensitiveto corrosion because there may be water surrounding the connector clampas well as electrical currents. The connector clamp may also comprise amovable part or bridge 57 which is moveable along the pair of arms toadjust a pressure applied to the plurality of current collectors betweenthe bridge 57 and the contact portion. Between fixed parts 55 andmovable part 57 a ratchet mechanism may be provided. For example, theratchet mechanism may comprise a surface with saw teeth which allowsmovement of the movable portion 55 in the direction of the connector butblocks movements of the movable portion 57 in opposite direction. Theelectrode may be provided in between the moveable portion 57 and thecontact surface 45. By pressing the moveable portion 57 against theelectrode and against the connector surface 45, a good connection willbe provided between the electrode and the cable 43. FIG. 6 shows a fullring 51 for the housing with two connectors 41. The contact surface maydefine a contact face having a contact plane and the current collectorof the electrode may be provided with an electrode plane which may besubstantially parallel to the contact plane. The opening 50 provided inthe ring 51 of the housing may define an elbow passage having a firstportion extending substantially perpendicular to a longitudinal axis ofthe housing and a second portion extending substantially parallel to thelongitudinal axis. The closing off portion or contact member 47 may beseated in the second portion.

FIG. 7 schematically depicts the capacitive electrode stack of FIG. 3wherein capacitive electrode stack A, B are provided with a tray 71A,71B. The tray 71A, 71B may improve manufacturability because it mayprotect the electrodes during assembling of the capacitive electrodestacks in the housing. During manufacturing of one capacitive electrodestack, the tray 71 may help in aligning the electrodes and/or thespacer. During use of the apparatus the tray may electrically and/orionically insulate one capacitive electrode stack from anothercapacitive electrode stack and counteract leak currents.

The capacitive electrode stacks may be clamped between a bottom plate 73and a pressure plate 75. A rod 77 may be provided through the opening 27of the stacks and a nut may be provided which in cooperation with athread on the rod may press the pressure plate 75 on the capacitiveelectrode stacks. Before pressing the pressure plate on the capacitiveelectrode stacks, water may be flushed through the spacer along theelectrodes. Flushing the stacks with water may comprise flowing waterthrough the stacks with a pressure of between 0.5 and 10 bar, between 1and 5 bar or between 2 and 4 bar. Flushing helps to remove any loosematerial out of the spacer and/or the membranes and/or the electrodesbefore the pressure is applied and after flushing, the capacitiveelectrode stack will be compressed and the capacitive electrode stackswill be fixed in the housing. The capacitive electrode stacks may befixated permanently. By exerting a force on the capacitive electrodestacks so as to compress the first and second electrodes and the spacer,the electrical resistivity may be decreased which may make the apparatusmore efficient. It is important that the electrical resistivity issubstantially equal for every capacitive electrode stack becauseotherwise the voltage is not equally divided over the individualcapacitive electrode stacks. If one capacitive electrode stack operatesat higher voltage than another capacitive electrode stack then thecapacitive electrode stack which receives a higher voltage may becomedamaged due to oxidation and/or electrolysis. Therefore the pressureneeds to be equally divided for all the capacitive electrode stacks. Thestacks may be compressed with pressure of less than 5 bar, less than 2bar, or between 1 bar and 0.5 bar.

The bottom plate 73 may form a part of the housing of the apparatus toremove ions. In FIG. 7 it is also shown how the electrode 13G may beprovided in between the moveable portion 57 and the closing off portion47 of the connector clamp 53 to be electrically connected to the cable43. A contact member may be seated in the base member or bottom plate 73to define a contact portion and a connector portion extends from thecontact portion. A lead may be engaged with the connector portion andcapable of directing an electrical current to the contact member. Aprotrusion member may be extending from the base member or bottom plate73 adjacent to the contact member. A compression member (similar as thedesign of FIG. 5) may be configured to selectively engage the protrusionmember at a plurality of positions relative to the contact member suchthat the compression member may be adjusted to compress a currentcollector of the electrode between the compression member and thecontact member. The compression member may include a resilient armhaving a first interlocking member and the protrusion member may includea second interlocking member. The first interlocking and secondinterlocking members are configured to selectively engage such thatfirst interlocking member of the compression member may be restrainedrelative to the contact member by the second interlocking member of theprotrusion member. The first interlocking member may define a pluralityof ramps and the second interlocking member may define a plurality ofinverse ramps. The plurality of ramps and the plurality of inverse rampsmay engage to inhibit separation of the protrusion member and thecompression member.

In FIG. 8 a first housing portion e.g., a round pipe section 81, isprovided to the bottom plate 73 and the ring 51 of FIG. 6 is located ontop of the section 81.

FIG. 9 schematically shows a cross section of the apparatus of FIGS. 3to 7 after a second round pipe section 91 is provided on top of the ring51, a second ring 93 is provided to the pipe section 91 and a top dome95 is provided to the apparatus. The housing may be made water tight byproviding flexible member 97, e.g., a rubber O-ring, in between thehousing portion and the ring 51 or between the housing portion 81 andthe bottom plate 73. The dome opening 101 in the top dome 95 allows forwater intake for example from a water pipe whereas opening 103 may beused for the water outlet. The dome opening 101 may also be used formaintenance of the stacks. For example a socket wrench may be allowedaccess through the dome opening 101 to tighten a nut cooperating with athread provided to the rod 77. By tightening the nut the capacitiveelectrode stacks may be compressed between the bottom plate 73 and thepressure plate 75. Before compressing the pressure plate on thecapacitive electrode stacks, water may be flushed through the spaceralong the electrodes. Flushing helps to remove any loose material out ofthe spacer and/or the membranes and/or the electrodes, after which thecapacitive electrode stack will be compressed.

It is advantageous that the dome opening 101 in the top dome 95 allowsfor compressing the stack while the housing is filled with water. Alsothe dome opening 101 allows for the pressure to be adjusted at a laterstage for example during installation of the apparatus or duringmaintenance. Further the connector 41 located in an opening 48 in thering 51 is shown. The clamp 53 presses the current collector of anelectrode onto the connector 41 and thereby presses the closing off body47 in the opening 48, thereby closing off the opening 48 for waterinside the housing.

FIG. 10A schematically depicts a pressure plate 75 according to anembodiment. The pressure plate 75 has a base 105 and a top portion 107.The top portion has an opening 103 to allow water to exit the stack(s).FIG. 10B schematically depicts how the pressure plate 75 of FIG. 10A maybe used to compress the capacitive electrode stacks together. Acompression member, for example a nut like object 109 may be accessedthrough the dome opening 101 to be tightened by rotating the nut likeobject with respect to the top dome 95. The nut like object 109 may beprovided with an external thread 111 to cooperate with an internalthread 113 of the top dome 95. By rotating the nut like object 109 thecapacitive electrode stacks may be compressed between the bottom plate73 and the pressure plate 75. The nut like object 109 may comprise holesto allow water to pass through and to provide grip to rotate the nutlike object 109. In the center of the nut like object 109, there is ahole in which the top portion 107 of the pressure plate 75 rotatablyfits.

The pressure plate 105 may have an interface between the housing and thepressure plate to inhibit a rotation of the pressure plate 105 relativeto the housing. The interface may have a projection extending from thepressure plate or the housing and a receiver formed in the other of thepressure plate or the housing to inhibit a rotation. The top portion maydefine an annular lip 110 and the compression member may define an endface. The end face of the compression member may engage the annular lip110 of the top portion to compress the stack.

Before compressing the pressure plate on the capacitive electrodestacks, water may be flushed through the spacer along the electrodes tohydrate the stack. Hydrating and/or flushing helps to remove any loosematerial out of the spacer, after which the capacitive electrode stackwill be compressed. It is advantageous that the dome opening 101 in thetop dome 95 allows for the compression to take place because thecapacitive electrode stack(s) may be compressed after the housing hasbeen filled with water. Also during maintenance the compression may beadjusted via the dome opening 101. The top dome 95 which is dome shapedmay include a neck that extends into the interior. Internal threads maybe formed on an interior surface of the neck; and external threads maybe formed on an exterior surface of the compression member. The internalthreads and the external threads are configured to engage, such thatrotation of the compression member around the longitudinal axis may movethe compression member along a longitudinal axis of the housing. Alongitudinal slit, receiver or a slot may be formed in the neck and aradial tab 108 may extend from the top portion 107 wherein thelongitudinal slit and the radial tab are configured to interface, suchthat rotation of the pressure plate 75 relative to the housing isinhibited.

FIG. 11A schematically shows a top view of a tray 113 a for use in anembodiment. The tray 113 a may comprise a main surface 115 to receive acapacitive electrode stack. The tray 113 a may have an opening 117 as analignment feature, which may be used to slide the tray along the rod 77(see FIG. 7) and to provide water to, or remove water from, the interiorof the capacitive electrode stack. The opening 117 may be constructedand arranged to cooperate with the rod 77, for example the size of theopening and the rod 77 may substantially match. The tray 113 a may haveadditional alignment features for alignment with the capacitiveelectrode stack, the rod, the housing, and/or other trays. Alignmentfeatures, such as protrusion 119, may be used to align the tray 113 awith the housing, or keep it at a constant distance from the housing.Another example of an alignment features may be tab 121 provided withteeth and provided to the first tray 113 a to interlock the tray with asecond tray positioned on top of the first tray 113 a. Surrounding theopening 117 there may be provided as alignment features first and secondpillar structure 123 a and 123 b respectively; both pillar structuresmay be provided with pillars and holes. The pillars 125 of the firstpillar structure 123 a may align with the holes 127 of a second pillarstructure provided to a second tray 113 b (see FIG. 11B). The tabs 121with teeth of the first tray 113 a may protrude through an opening inthe second tray 113 b and the teeth of the first tray may interlock withan edge of the opening of the second tray 113 b. A spring 129 (see FIG.11C) may be provided to the tab 121 of the second tray 113 b to pressthe teeth (not shown) against the edge 131. FIG. 11D shows how the teethof the tab 121 interlock with second tray 113 b.

Further, a first electrode 133 is shown. The electrode comprises a firstcurrent collector 135 and is positioned within the tray and aligned bythe alignment features of the second tray 113 b. The first currentcollector 135 protrudes outside the second tray 113 b so that it may beconnected to other current collectors. The second tray 113 b maycomprise an opening 137 which may interlock with a clamp (not shown)which clamps the first current collector of the second tray 113 b to thesecond current collector of another tray. The trays may function as anelectrical insulator between capacitive electrode stacks. Byinterlocking a number of trays each provided with a capacitive electrodestack and by connecting the current collectors to each other thecapacitive electrode stack may be assembled together.

Subsequently the capacitive electrode stacks may be put into a housingand flushed with water. After flushing the capacitive electrode stacks,the stacks may be compressed by rotating the nut like object 109 of FIG.10 and the capacitive electrode stacks may be compressed between thebottom plate 73 and the pressure plate 75.

While specific embodiments of the invention have been described above,it will be appreciated that the invention may be practiced otherwisethan as described. For example, the invention may take the form of acomputer program containing one or more sequences of machine-readableinstructions describing a method as disclosed above, or a data storagemedium (e.g. semiconductor memory, magnetic or optical disk) having sucha computer program stored therein.

Embodiments are also provided in the following numbered clauses:

1. An apparatus to remove ions comprises a plurality of capacitiveelectrode stacks, each capacitive electrode stack comprising:

a first electrode comprising a first current collector;

a second electrode comprising a second current collector; and

a spacer between the first and second electrodes to allow water to flowin between the electrodes,

wherein the second current collector of a first of the plurality ofcapacitive electrode stacks is directly connected to the first currentcollector of a second of the plurality of capacitive electrode stacks.

2. The apparatus according to the preceding clause, wherein the secondcurrent collector of the second of the plurality of capacitive electrodestacks is in direct electrical connection to the first current collectorof a third of the plurality of capacitive electrode stacks.3. The apparatus according to any of the preceding clauses, furthercomprising a housing and the apparatus comprising:

-   -   an inlet to let water enter an interior of the housing; and    -   an outlet to let water out of the interior of the housing,    -   wherein the second current collector of the first of the        plurality of capacitive electrode stacks is directly connected        to the first current collector of the second of the plurality of        capacitive electrode stacks within the same housing.        4. The apparatus according to any of the preceding clauses,        wherein the first and second current collectors are directly        connected by pressing them against each other.        5. The apparatus according to any of the preceding clauses,        further comprising a clamp to press the current collectors        against each other.        6. The apparatus according to clause 5, wherein the clamp is of        a non-metal material.        7. The apparatus according to any of the preceding clauses,        wherein the current collectors are metal free.        8. The apparatus according to any of the preceding clauses,        wherein the current collectors comprise carbon to conduct an        electrical charge.        9. The apparatus according to any of the preceding clauses,        further comprising a power connector for connection with a power        supply and the stacks are in connected in series with the power        connector.        10. The apparatus according to clause 9, wherein the power        connector is connected in series to a first current collector of        a first of the plurality of capacitive electrode stacks and to a        second current collector of the last of the plurality of        capacitive electrode stacks.        11. The apparatus according to clause 9 or clause 10, wherein        the power connector comprises a metal and a carbon portion.        12. The apparatus according to clause 11, further comprising a        power connector clamp configured to press the current collector        against the carbon portion of the power connector.        13. The apparatus according to any of the preceding clauses,        further comprising an insulator between each capacitive        electrode stack so to electrically insulate both stacks from        each other.        14. The apparatus according to clause 13, wherein the insulator        comprises a tray configured to hold the stack.        15. The apparatus according to clause 14, further comprising a        second insulator substantially surrounding the current collector        so as to electrically insulate the current collector.        16. The apparatus according to any of clauses 9 to 15,        comprising a housing and the apparatus comprises:

an inlet to let water enter an interior of the housing; and

an outlet to let water out of the interior of the housing,

wherein the power connector provides an electrical connection betweenthe current collector and the outside of the housing.

17. The apparatus according to any of the preceding clauses, whereineach capacitive electrode stack comprises:

a plurality of first electrodes comprising a plurality of first currentcollectors; and

a plurality of second electrodes comprising a plurality of secondcurrent collectors,

wherein the second current collectors of a first of the plurality ofcapacitive electrode stacks are directly connected to the first currentcollectors of a second of the plurality of capacitive stacks.

18. The apparatus according to clause 17, wherein the plurality ofcurrent collectors within the electrode stack are connected in parallel.

19. An apparatus to remove ions comprising:

a plurality of capacitive electrode stacks, each electrode capacitiveelectrode stack comprising:

a first electrode comprising a first current collector,

a second electrode comprising a second current collector, and

a spacer between the first and second electrodes to allow water to flowin between the electrodes; and

a power connector configured to connect a power source to a plurality ofthe capacitive electrode stacks in electrical serial connection witheach other,

wherein the resistivity in each of the capacitive electrode stacks issubstantially equal so as to divide the potential difference of thepower source substantially equally over all capacitive electrode stacks.

20. The apparatus according to clause 19, further comprising a housingand the apparatus comprising:

an inlet to let water enter an interior of the housing; and

an outlet to let water out of the interior of the housing,

wherein the capacitive electrode stacks are serially connected withinthe housing.

21. The apparatus according to clause 19 or clause 20, wherein theelectrical current going through the second electrode of the firstcapacitive electrode stack is equal to the electrical current going intothe first electrode of the second capacitive electrode stack.22. The apparatus according to any of clauses 19 to 21, wherein thecapacitive electrode stacks that are in electrical serial connectionwith each other are placed in a same housing.23. The apparatus according to any of clauses 19 to 22, wherein thesecond current collector of the first of the plurality of capacitiveelectrode stacks is directly connected to the first current collector ofthe second of the plurality of capacitive electrode stacks.24. The apparatus according to any of clauses 19 to 23, furthercomprising a pressure device configured to provide a pressure to thestacks such that the pressure for each of the stack is equal.25. A method for manufacturing an apparatus to remove ions, the methodcomprising:

providing a plurality of capacitive electrode stacks, each capacitiveelectrode stack manufactured by:

providing a first electrode comprising a first current collector;

providing a second electrode comprising a second current collector; and

providing a spacer between the first and second electrodes to allowwater to flow in between the electrodes,

connecting the second current collector of a first of the plurality ofcapacitive electrode stacks to the first current collector of a secondof the plurality of capacitive electrode stacks.

26. An apparatus to remove ions, the apparatus comprising a housing andthe apparatus comprising:

an inlet to let water enter an interior of the housing;

an outlet to let water out of the interior of the housing;

a first electrode comprising a current collector;

a second electrode;

a spacer to separate the electrodes and allow water to flow in betweenthe electrodes; and

a connector to connect the current collector inside the housing with anelectrical source outside the housing, wherein the connector comprises aclosing off portion configured to close an opening in the housing and toform a boundary for the water in the housing.

27. The apparatus according to clause 26, wherein the current collectoris pressed against a substantially flat surface of the connector.

28. The apparatus according to clause 26 or clause 27, wherein theconnector is pressed against the housing.

29. The apparatus according to any of clauses 26 to 28, furthercomprising a flexible material between the connector and the opening soas to close the opening off in a water tight manner.

30. The apparatus according to any of clauses 26 to 29, wherein theclosing off portion is made from a material comprising carbon.

31. The apparatus according to clause 30, wherein the material comprisesgraphite.

32. The apparatus according to clause 30, wherein the material comprisesa conductive polymer.

33. The apparatus according to any of clauses 26 to 32, wherein theconnector comprises a metal portion connecting to a connector portion ata dry surface of the connector portion.

34. The apparatus according to clause 33, wherein the connector portioncomprises a hole in the dry surface and the metal portion enters theconnector portion through the hole.

35. The apparatus according to any of clauses 26 to 34, furthercomprising a clamp to press the electrode against the closing offportion of the connector.

36. The apparatus according to clause 35, wherein the clamp comprises astationary part and a moveable part and the moveable part is moveableagainst the electrode to press the electrode against the closing offportion of the connector.

37. The apparatus according to clause 36, wherein the moveable andstationary parts of the clamp are constructed and arranged so that themoveable part is moveable in a first direction but blocked in anopposite direction.

38. A capacitive deionization device, comprising:

a housing defining an opening between an interior of the housing and anexterior of the housing;

a stack within the housing;

a contact member seated in the opening and defining a contact portionadjacent to the interior of the housing and a connector portion adjacentto the exterior of the housing; and

a lead engaged with the connector portion and capable of directing anelectrical current to the contact member,

wherein the contact portion is configured to engage the stack such thatthe contact member is in electrical communication with the stack.

39. The capacitive deionization device of clause 38, wherein the contactportion is substantially cylindrical and defines a contact face, and aperimeter of the contact face forms an arcuate rim.

40. The capacitive deionization device of clause 38, wherein:

the contact portion defines a contact face having a rim about aperimeter of the contact face; and

the contact face includes a recess inward of the perimeter, and aprotrusion extending from the recess that terminates substantiallycoplanar with the rim.

41. The capacitive deionization device of clause 40, wherein the contactface is substantially circular and the protrusion is substantiallycylindrical.

42. The capacitive deionization device of clause 38, wherein theconnector portion is substantially cylindrical and a receptacle isformed in the connector portion such that the lead is engaged within thereceptacle.

43. The capacitive deionization device of clause 38, wherein the housingfurther defines a recess proximate the opening and the contact portionof the contact member is seated in the recess.

44. The capacitive deionization device of clause 38, wherein the contactmember is press fit in the opening and/or adhered in the opening.

45. The capacitive deionization device of clause 38, further comprisinga seal formed between the contact member and the opening such that afluid within the interior of the housing is inhibited from flowingthrough the opening toward the exterior of the housing.46. The capacitive deionization device of clause 45, wherein the sealincludes an O-ring seated in an annular channel formed in a radial faceof the contact portion.47. The capacitive deionization device of clause 38, further comprising:

a plurality of electrodes within the stack;

a protrusion member extending from an interior surface of the housing;and

a compression member configured to selectively engage the protrusionmember at a plurality of positions relative to the contact member suchthat the compression member may be adjusted to compress the plurality ofelectrodes between the compression member and the contact portion of thecontact member.

48. The capacitive deionization device of clause 47, wherein:

the protrusion member includes a pair or arms;

the compression member includes a bridge spanning between the pair orarms; and

the bridge is moveable along the pair of arms to adjust a pressureapplied to the plurality of electrodes between the bridge and thecontact portion.

49. The capacitive deionization device of clause 38, wherein:

the stack includes an electrode having an electrode plane;

the contact portion defines a contact face having a contact plane; and

the electrode plane and the contact plane are substantially parallel.

50. The capacitive deionization device of clause 38, wherein:

the opening defines an elbow passage having a first portion extendingsubstantially perpendicular to a longitudinal axis of the housing and asecond portion extending substantially parallel to the longitudinalaxis; and

the contact member is seated in the second portion.

51. The capacitive deionization device of clause 38, wherein the contactmember is at least partially formed of graphite.

52. An electrical connector assembly, comprising:

a base member;

a contact member seated in the base member and defining a contactportion and a connector portion extending from the contact portion;

a lead engaged with the connector portion and capable of directing anelectrical current to the contact member;

a protrusion member extending from the base member adjacent to thecontact member; and

a compression member configured to selectively engage the protrusionmember at a plurality of positions relative to the contact member suchthat the compression member may be adjusted to compress an electrodebetween the compression member and the contact member.

53. The electrical connector assembly of clause 52, wherein:

the contact portion is substantially cylindrical and defines a contactface; and

a perimeter of the contact face forms an arcuate rim.

54. The electrical connector assembly of clause 52, wherein:

the contact portion defines a contact face having a rim about aperimeter of the contact face; and

the contact face includes a recess inward of the perimeter, and aprotrusion extending from the recess that terminates substantiallycoplanar with the rim.

55. The electrical connector assembly of clause 54, wherein:

the contact face is substantially circular; and

the protrusion is substantially cylindrical.

56. The electrical connector assembly of clause 52, wherein:

the connector portion is substantially cylindrical; and

a receptacle is formed in the connector portion such that the lead isengaged within the receptacle.

57. The electrical connector assembly of clause 52, wherein:

the base member defines a recess; and

the contact portion of the contact member is seated in the recess.

58. The electrical connector assembly of clause 57, wherein the contactmember is press fit in the recess and/or adhered in the recess.

59. The electrical connector assembly of clause 57, further comprising aseal formed between the contact member and the recess such that a fluidis inhibited from flowing past the seal.

60. The electrical connector assembly of clause 59, wherein the sealincludes an O-ring seated in an annular channel formed in a radial faceof the contact portion.

61. The electrical connector assembly of clause 52, wherein:

the protrusion member includes a pair of arms;

the compression member includes a bridge spanning between the pair ofarms; and

the bridge is moveable along the pair of arms to adjust a pressureapplied to the electrode between the bridge and the contact portion ofthe contact member.

62. The electrical connector assembly of clause 52, wherein:

the compression member includes a resilient arm having a firstinterlocking member; and

the protrusion member includes a second interlocking member;

wherein the first interlocking member and the second interlocking memberare configured to selectively engage such that first interlocking memberof the compression member may be restrained relative to the contactmember by the second interlocking member of the protrusion member.

63. The electrical connector assembly of clause 62, wherein:

the first interlocking member defines a plurality of ramps;

the second interlocking member defines a plurality of inverse ramps;

the plurality of ramps and the plurality of inverse ramps engage toinhibit separation of the protrusion member and the compression member.

64. The electrical connector assembly of clause 52, wherein:

the contact portion defines a contact plane;

the compression member defines a compression plane; and

the contact plane and the compression plane are substantially parallel.

65. The electrical connector assembly of clause 52, wherein:

the base member includes an opening that defines an elbow passage havinga first portion extending substantially perpendicular to a wall of thebase member and a second portion extending substantially parallel to thewall; and

the contact member is seated in the second portion.

66. The electrical connector assembly of clause 52, wherein the contactmember is at least partially formed of graphite.

67. An electrical connector, comprising:

a contact portion having a head that defines a contact face;

a connector portion having a neck extending from the head in a directionaway from the contact face;

a lead engaged with the neck and capable of directing an electricalcurrent to the head; and

a seal portion defined by the head and/or the neck such that the sealportion establishes a hydraulic seal between the seal portion and amount into which the electrical connector is seated during operation.

68. The electrical connector of clause 67, wherein:

the head is substantially cylindrical; and

the neck is substantially cylindrical.

69. The electrical connector of clause 67, wherein a perimeter of thecontact face forms an arcuate rim.

70. The electrical connector of clause 67, wherein the contact facefurther comprises:

a rim about a perimeter of the contact face;

a recess inward of the perimeter; and

a protrusion extending from the recess that terminates substantiallycoplanar with the rim.

71. The electrical connector of clause 70, wherein:

the contact face is substantially circular; and

the protrusion is substantially cylindrical.

72. The electrical connector of clause 67, wherein:

the connector portion is substantially cylindrical; and

a receptacle is formed in the neck such that the lead is engaged withinthe receptacle.

73. The electrical connector of clause 67, wherein the seal portion isdefined by the head.

74. The electrical connector of clause 73, wherein the seal portionincludes:

an annular channel formed in a radial face of the head; and

an O-ring seated in the annular channel.

75. The electrical connector of clause 67, wherein the head defines anannular mounting face opposite to the contact face.

76. The electrical connector of clause 67, wherein the contact portionis at least partially formed of graphite.

77. The electrical connector of clause 76, wherein the connector portionis at least partially formed of graphite.

78. The electrical connector of clause 67, wherein the contact portionand the connector portion are integral.

79. A capacitive deionization device, comprising:

a housing defining an opening;

a stack within the housing;

a pressure plate within the housing and adjacent to the stack; and

a compression member within the opening and adjacent to the pressureplate,

wherein the compression member engages the housing and the pressureplate such that moving the compression member relative to the housingurges the pressure plate toward the stack to compress the stack.

80. The capacitive deionization device of clause 79, further comprising:

a first fluid passage formed through the compression member and in fluidcommunication with the opening; and

a second fluid passage formed through the pressure plate and in fluidcommunication with the opening.

81. The capacitive deionization device of clause 79, further comprisingan interface between the housing and the pressure plate that inhibitsrotation of the pressure plate relative to the housing.

82. The capacitive deionization device of clause 81, wherein theinterface comprises:

a projection extending from the pressure plate or the housing; and

a receiver formed in the other of the pressure plate or the housing.

83. The capacitive deionization device of clause 79, further comprising:

internal threads formed on an interior surface of the opening; and

external threads formed on an exterior surface of the compressionmember,

wherein the internal threads and the external threads are configured toengage, such that rotation of the compression member relative to thehousing moves the compression member along an axis of the housing.

84. The capacitive deionization device of clause 79, wherein rotatingthe compression member relative to the housing adjusts the compressionmember to alter a position of the pressure plate.

85. The capacitive deionization device of clause 79, wherein the stackcomprises a plurality of stacks.

86. A capacitive deionization device, comprising:

a housing, the housing including:

-   -   a first end; and    -   a second end opposite to the first end;

a stack arranged within the housing, the stack including:

-   -   a first electrode;    -   an anion member adjacent to the first electrode;    -   a second electrode;    -   a cation member adjacent to the second electrode; and    -   a spacer between the anion member and the cation member;

a pressure plate adjacent to the stack, the pressure plate including:

-   -   a base; and    -   a top portion extending from the base; and

a compression member proximate to the pressure plate and the housing,

wherein the compression member engages the top portion of the pressureplate and the first end of the housing, such that the compression membermay be adjusted to alter a position of the pressure plate relative tothe first end of the housing to compress the stack toward the second endof the housing.

87. The capacitive deionization device of clause 86, wherein rotatingthe compression member relative to the housing adjusts the compressionmember to alter the position of the pressure plate relative to the firstend of the housing.

88. The capacitive deionization device of clause 86, wherein:

the housing defines internal threads; and

the compression member defines external threads configured to threadablyengage the internal threads of the housing.

89. The capacitive deionization device of clause 86, wherein:

the top portion defines an annular lip;

the compression member defines an end face; and

the end face of the compression member engages the annular lip of thetop portion to compress the stack toward the second end of the housingwhen the compression member is adjusted.

90. The capacitive deionization device of clause 86, further comprising:

an opening formed through the first end of the housing;

a first fluid passage formed through the compression member and in fluidcommunication with the opening; and

a second fluid passage formed though the pressure plate, and in fluidcommunication with the opening,

wherein the first fluid passage defines a fluid inlet directinguntreated fluid into the housing; and

wherein the second fluid passage defines a fluid outlet directingtreated water from the housing.

91. The capacitive deionization device of clause 86, further comprisingan interface between the housing and the pressure plate, such that theinterface inhibits rotation of the pressure plate relative to thehousing.

92. The capacitive deionization device of clause 91, wherein theinterface comprises:

a projection extending from the top portion of the pressure plate; and

a receiver formed in the first end of the housing.

93. The capacitive deionization device of clause 86, further comprisingan interior defined between the first end and the second end of thehousing, wherein the first end is dome-shaped and includes a neck thatextends into the interior.

94. The capacitive deionization device of clause 93, further comprising:

internal threads formed on an interior surface of the neck; and

external threads formed on an exterior surface of the compressionmember,

wherein the internal threads and the external threads are configured toengage, such that rotation of the compression member moves thecompression member along a longitudinal axis of the housing.

95. The capacitive deionization device of clause 94, further comprising:

a longitudinal slit formed in the neck; and

a radial tab extending from the top portion,

wherein the longitudinal slit and the radial tab are configured tointerface, such that rotation of the pressure plate relative to thehousing is inhibited.

96. The capacitive deionization device of clause 86, wherein the stackcomprises a plurality of stacks.

97. A capacitive deionization device, comprising:

a housing defining a longitudinal axis;

a stack within the housing;

a pressure plate within the housing and adjacent to the stack;

a compression member engaged with the housing and adjacent to thepressure plate, such that movement of the compression member relative tothe housing urges the pressure plate along the longitudinal axis towardthe stack; and

an interface between the housing and the pressure plate that inhibitsrotation of the pressure plate relative to the housing.

98. The capacitive deionization device of clause 97, wherein theinterface comprises:

a projection extending from the pressure plate or the housing; and

a receiver formed in the other of the pressure plate or the housing.

99. The capacitive deionization device of clause 97, wherein theinterface comprises:

a tab radially extending from the pressure plate; and

a slot formed in the housing,

wherein the tab is sized to seat within the slot, such that the pressureplate is inhibited from rotation relative to the housing as the tab ofthe pressure plate abuts the slot of the housing.

100. The capacitive deionization device of clause 97, wherein:

the housing defines internal threads;

the compression member defines external threads configured to threadablyengage the internal threads of the housing; and

rotation of the compression member urges the pressure plate along thelongitudinal axis toward the stack.

101. The capacitive deionization device of clause 100, wherein:

the compression member rotates about the longitudinal axis; and

the compression member directly engages the pressure plate.

102. The capacitive deionization device of clause 97, furthercomprising:

an opening formed through the housing;

a first fluid passage formed through the compression member and in fluidcommunication with the opening; and

a second fluid passage formed through the pressure plate and in fluidcommunication with the opening.

103. The capacitive deionization device of clause 102, wherein theopening and the second fluid passage are concentric and axially alignedwith the longitudinal axis.

104. The capacitive deionization device of clause 97, wherein rotatingthe compression member relative to the housing adjusts the compressionmember to alter a position of the pressure plate.

105. A capacitive deionization device, comprising:

a housing defining an opening between an interior of the housing and anexterior of the housing;

a stack within the housing;

a pressure plate within the housing and adjacent to the stack;

a compression member engaged with the housing and adjacent to thepressure plate;

a first fluid passage formed through the compression member andextending into the opening of the housing; and

a second fluid passage formed through the pressure plate and extendinginto the opening of the housing,

wherein moving the compression member relative to the housing urges thepressure plate toward the stack to compress the stack;

wherein the first fluid passage defines a fluid inlet directinguntreated fluid from the exterior to the interior of the housing or afluid outlet directing treated water from the interior to the exteriorof the housing, and

wherein the second fluid passage defines the other of the fluid inlet orthe fluid outlet.

106. The capacitive deionization device of clause 105, furthercomprising:

internal threads formed on an interior surface of the opening; and

external threads formed on an exterior surface of the compressionmember,

wherein the internal threads and the external threads are configured toengage, such that rotation of the compression member urges the pressureplate toward the stack.

107. The capacitive deionization device of clause 105, wherein rotatingthe compression member relative to the housing adjusts the compressionmember to alter a position of the pressure plate.

108. The capacitive deionization device of clause 105, wherein theopening and the second fluid passage are concentric.

109. The capacitive deionization device of clause 105, furthercomprising an interface between the housing and the pressure plate thatinhibits rotation of the pressure plate relative to the housing.

110. The capacitive deionization device of clause 109, wherein theinterface comprises:

a projection extending from the pressure plate or the housing; and

a receiver formed in the other of the pressure plate or the housing.

111. The capacitive deionization device of clause 105, wherein:

the compression member is cylindrical, and defines an interior surfaceand an exterior surface; and

the first fluid passage comprises a plurality of fluid passages radiallyspaced about the compression member and formed between the interiorsurface and the exterior surface.

112. The capacitive deionization device of clause 111, wherein theexterior surface of the compression member defines external threads thatare configured to engage internal threads formed on an interior surfaceof the opening.

113. A method of using a capacitive deionization device, the methodcomprising:

providing a housing defining an opening between an interior of thehousing and an exterior of the housing;

positioning a stack in the interior of the housing;

orienting a pressure plate in the interior of the housing and adjacentto the stack;

engaging a compression member with the housing and the pressure plate;

adjusting the compression member relative to the housing to urge thepressure plate toward the stack to compress the stack with the pressureplate; and

hydrating the stack by directing fluid through the opening.

114. The method of clause 113, wherein the compression member isadjusted after hydrating the stack.

115. The method of clause 113, wherein adjusting the compression memberincreases a pressure applied to the stack by the pressure plate.

116. The method of clause 113, further comprising a first fluid passageformed through the compression member, wherein hydrating the stackincludes directing the fluid into the first passage.

117. A method of producing an apparatus to remove ions from water, themethod comprising:

providing a first electrode;

providing a spacer against the first electrode;

providing a second electrode against the spacer; and

flushing water through the spacer and subsequently exerting a force onthe stack so as to compress the first and second electrodes and thespacer.

118. The method according to clause 117, wherein the steps of: providinga first electrode;

providing a spacer against the first electrode;

providing a second electrode against the spacer; and

providing a spacer against the second electrode, are repeated multipletimes.

119. The method according to clause 117 or clause 118, wherein exertinga force results in a pressure of less than 5 bar, less than 2 bar, orbetween 1 bar and 0.5 bar, between the electrodes and the spacer.

120. The method according to any of clauses 117 to 119, furthercomprising providing a tray to hold the electrodes and the spacer.

121. The method according to any of clauses 117 to 120, furthercomprising aligning the electrodes and the spacer with each other.

122. The method according to any of clauses 117 to 121, wherein flushingwater through the spacer comprises flushing with a pressure of between0.5 and 10 bar, between 1 and 5 bar or between 2 and 4 bar.

123. The method according to any of clauses 117 to 122, furthercomprising providing the electrodes and the spacer in a housing, thehousing comprising an inlet and an outlet opening, and providing waterto the housing via the inlet opening for flushing water through thespacer.124. The method according to any of clauses 117 to 123, wherein exertinga force so as to compress the first and second electrodes and the spacercomprises providing a first pressure plate against one side of a stackformed by the electrodes and the spacer and a second pressure plateagainst the other side of the stack, providing a rod through all theelectrodes and spacers and exerting a force on the first and secondpressure plates via the rod to compress the stack in between the plates.125. The method according to any of clauses 117 to 124, wherein thefirst and second electrodes comprise current collectors and some currentcollectors may be connected together before compressing the first andsecond electrodes and the spacer.

The descriptions above are intended to be illustrative, not limiting.Thus, it will be apparent to one skilled in the art that modificationsmay be made to the invention as described without departing from thescope of the claims set out below.

The invention claimed is:
 1. A capacitive deionization device,comprising: a housing defining an opening; a capacitive deionizationstack within the housing; a pressure plate within the housing andadjacent to the capacitive deionization stack; and a compression memberwithin the opening and adjacent to the pressure plate, wherein thecompression member is configured to engage the housing and the pressureplate such that a movement of the compression member relative to thehousing urges the pressure plate toward the capacitive deionizationstack to compress the capacitive deionization stack.
 2. The device ofclaim 1, further comprising: a first fluid passage formed through thecompression member and in fluid communication with the opening; and asecond fluid passage formed through the pressure plate and in fluidcommunication with the opening.
 3. The device of claim 1, furthercomprising an interface between the housing and the pressure plate,configured to inhibit rotation of the pressure plate relative to thehousing.
 4. The device of claim 3, wherein the interface comprises: aprojection extending from either the pressure plate or the housing; anda receiver of the projection, formed in the other of the pressure plateor the housing.
 5. The device of claim 1, further comprising: internalthreads formed on an interior surface of the opening; and externalthreads formed on an exterior surface of the compression member, whereinthe internal threads and the external threads are configured to engage,such that a rotation of the compression member relative to the housingmoves the compression member along an axis of the housing.
 6. The deviceof claim 1, wherein the compression member is configured such that arotation of the compression member relative to the housing adjusts thecompression member to alter a position of the pressure plate.
 7. Acapacitive deionization device, comprising: a housing including a firstend and a second end opposite to the first end; a capacitivedeionization stack arranged within the housing; a pressure plateadjacent to the capacitive deionization stack, the pressure plateincluding a base and a top portion extending from the base; and acompression member proximate to the pressure plate and the housing,wherein the compression member is configured to engage the top portionof the pressure plate and the first end of the housing, such that anadjustment of the compression member alters a position of the pressureplate relative to the first end of the housing to compress thecapacitive deionization stack toward the second end of the housing. 8.The device of claim 7, wherein the compression member is configured suchthat a rotation of the compression member relative to the housingadjusts the compression member to alter the position of the pressureplate relative to the first end of the housing.
 9. The device of claim7, wherein: the housing defines internal threads; and the compressionmember defines external threads configured to threadably engage theinternal threads of the housing.
 10. The device of claim 7, wherein: thetop portion defines an annular lip; the compression member defines anend face; and the end face of the compression member is configured toengage the annular lip of the top portion to compress the capacitivedeionization stack toward the second end of the housing when thecompression member is adjusted.
 11. The device of claim 7, furthercomprising: an opening formed through the first end of the housing; afirst fluid passage formed through the compression member and in fluidcommunication with the opening; and a second fluid passage formed thoughthe pressure plate, and in fluid communication with the opening, whereinthe first fluid passage defines a fluid inlet directing untreated fluidinto the housing, and wherein the second fluid passage defines a fluidoutlet directing treated fluid from the housing.
 12. The device of claim7, further comprising an interface between the housing and the pressureplate, configured to inhibit rotation of the pressure plate relative tothe housing.
 13. The device of claim 12, wherein the interfacecomprises: a projection extending from either the pressure plate or thehousing; and a receiver of the projection, formed in the other of thepressure plate or the housing.
 14. The device of claim 7, furthercomprising an interior defined between the first end and the second endof the housing, wherein the first end is dome-shaped and includes a neckthat extends in the interior.
 15. The device of claim 14, furthercomprising: internal threads formed on an interior surface of the neck;and external threads formed on an exterior surface of the compressionmember, wherein the internal threads and the external threads areconfigured to engage, such that a rotation of the compression membermoves the compression member along a longitudinal axis of the housing.16. The device of claim 14, further comprising: a longitudinal slitformed in the neck; and a radial tab extending from the top portion,wherein the longitudinal slit and the radial tab are configured tointerface, such that rotation of the pressure plate relative to thehousing is inhibited.
 17. A capacitive deionization device, comprising:a housing defining a longitudinal axis; a capacitive deionization stackarranged within the housing; a pressure plate within the housing andadjacent to the capacitive deionization stack; a compression memberengaged with the housing and adjacent to the pressure plate, thecompression member configured such that a movement of the compressionmember relative to the housing urges the pressure plate along thelongitudinal axis toward the capacitive deionization stack; and aninterface between the housing and the pressure plate, configured toinhibit rotation of the pressure plate relative to the housing.
 18. Thedevice of claim 17, wherein the interface comprises: a projectionextending from either the pressure plate or the housing; and a receiverof the projection, formed in the other of the pressure plate or thehousing.
 19. The device of claim 17, wherein the interface comprises: atab radially extending from the pressure plate; and a slot formed in thehousing, wherein the tab is sized to seat within the slot, such that thepressure plate is inhibited from rotation relative to the housing as thetab of the pressure plate abuts the slot of the housing.
 20. The deviceof claim 17, wherein: the housing defines internal threads; and thecompression member defines external threads configured to threadablyengage the internal threads of the housing, wherein the compressionmember is configured such that a rotation of the compression memberurges the pressure plate along the longitudinal axis toward thecapacitive deionization stack.